It is well known that color images are formed when exposed silver halides are used as oxidants and couplers and oxidized primary aromatic amine-based color developers react to produce indophenol, indoaniline, indamine, azomethine, phenoxazine, phenazine and other similar dyes.
Of these, 5-pyrazolone, cyanoacetophenone, indazolone, pyrazolobenzimidazole and pyrazolotriazole based couplers are used to form magenta images.
Hitherto, it has largely been the 5-pyrazolones for which studies have been most advanced and which have been most widely supplied as magenta color image forming couplers. However, it is known that with dyes formed by 5-pyrazolone-based couplers, there is unwanted absorption having a yellow component in the vicinity of 430 nm and that this is a cause of color contamination.
By way of magenta color image forming skeletons in which this yellow component has been reduced, there have been proposals for a pyrazolobenzimidazole skeleton as described in G.B. Patent 1,047,612, an indazolone skeleton as described in U.S. Pat. No. 3,770,447 and a pyrazolo[5,1-c]-1,2,4-triazole skeleton as described in U.S. Pat. No. 3,725,067.
However, the magenta couplers described in these patents are still unsatisfactory in that, when they are mixed into the silver halide emulsion in a form whereby they have been dispersed in a protective hydrophilic colloid such as gelatin, they provide no more than an unsatisfactory color image, their solubility in high-boiling organic solvents is poor, they are difficult to synthesize, they have no more than a relatively low coupling activity in common developers and the light fastness of the dye is extremely low.
As a result of diverse studies into novel types of magenta color image couplers which do not exhibit secondary absorption in the vicinity of 430 nm, which is the largest problem in terms of the hue of 5-pyrazolone-based couplers, the present inventors discovered the 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers disclosed in JP-A-59-171956 (the term "JP-A" as used herein means an "unexamined Japanese patent application") and U.S. Pat. No. 4,540,654 which do not exhibit secondary absorption on the shorter wavelength side, for which the fastness of the dye is high and which are easy to synthesize. These couplers have the distinguishing features that they are outstanding in terms of color reproduction and outstanding in their synthesizability, that they can be made what is known as 2-equivalent by introducing an eliminating group in the coupling active position and it is possible to reduce the amount of silver used.
Nevertheless, there are the problems that the color-forming property of these couplers is low and that there are major changes in photographic properties which accompany variations in processing solution constituent concentrations during continuous processing (for example sulfite ions, hydroxylamine derivatives and the like which are added to developing solutions as antioxidants for color developing agents).
The 1H-pyrazolo[5,1-c]-1,2,4-triazole and 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers in which the 6-position has been substituted with an alkyloxy group or an aryloxy group as described in JP-A-62-209457 are known as means of overcoming these problems, and it is understood that the color-forming properties are improved and that variations in the photographic properties during continuous processing are markedly inhibited when using these couplers However there are the problems that staining (an increase in the density of white-base portions) is exacerbated by aging after processing and that the light fastness of the azomethine dyes which are formed from these couplers is markedly reduced.
Staining is undesirable in silver halide color photographic materials not only because it determines the quality of the transparent image portion of the image but also because it worsens the color in the color image and detracts from the visual sharpness. With reflective materials (such as color papers) in particular, the reflected density of the stain will in theory be accentuated to several times the transmitted density and even the slightest of stains detracts from the picture quality, which constitutes a major problem.
Improvements which make use of the addition of various compounds are undertaken to resolve such problems. For example, JP-B-57-20617 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-58-114036, JP-A-59-53846, JP-A-59-4-78344, JP-A-59-109052, JP-A-59-113441, JP-A-59-119351, JP-A-59-133543, JP-A-61-4045, JP-A-62-178241, JP-A-62-161150, European Patent 242,211 and other such patents disclose methods using hindered amine-based derivatives and hindered amine-based derivatives which have a hindered phenol within the molecule However, with the compounds actually described in these patents, the prevention of damp heat staining and of light fading of the dye by the couplers of the inventions is insufficient and some even exert an adverse influence on the photographic properties. Furthermore, JP-A-62-92945, JP-A-62-96944 and JP-A-63-231340 describe examples in which hindered amine-based derivatives are applied to pyrazoloazole-based couplers, but the couplers of these inventions did not exhibit an adequate effect. Moreover, European Patent 218,266 describes similar examples but adequate effects were not exhibited by the couplers actually described in this patent. Again, although the hindered amine-based derivatives described in Japanese Patent Application No. 62-309497 exhibit an effect on stain prevention, they exert an adverse influence on photographic properties such as the speed and color-forming properties and these are not satisfactory compounds. Furthermore, by way of examples in which the light fading of pyrazoloazole couplers is improved by the joint use of two different compounds, there have been disclosures of methods involving the joint use of a hindered amine-based derivative and a hydroquinone derivative as described in JP-A-62-180367, and the joint use of a hindered amine-based derivative and a metal complex as described in JP-A-62-183459. However, even though color fading by light is slightly improved with these methods, they have no effect on damp heat staining and many of them also have an adverse effect on the photographic properties.
In general, pyrazoloazole-based magenta couplers are liable to produce magenta staining upon aging due to chemicals remaining after processing. Compounds for preventing the occurrence of such magenta staining are disclosed in European Patents 255,722, 258,662 and 277,589. These compounds have an effect on the magenta stain which is produced by the remaining chemicals but they are insufficient to prevent the stain (yellowing) which occurs when the couplers degrade
With this in mind, there is a desire for techniques which inhibit the increase in stain and inhibit color fading by light and which do not have any adverse effect on the photographic properties.
Accordingly, an object of this invention is to use a pyrazoloazole magenta coupler with an outstanding hue and outstanding color-forming properties to provide color photographic materials with which the color reproduction is outstanding and the increase in stain of the white-base is inhibited and which provide color images with outstanding light fastness.
Another objective of this invention is to provide color photographic materials in which there is essentially no occurrence of the changes in photographic properties which can occur due to aging after taking a photograph.